Relief-type production



(No Model.)

J. W. HOKE.

RELIEF TYPE PRODUGTION.

No. 388,361. Patented Aug. 21, 1888.

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JOSEPH W. HOKE, OF ST. LOUIS, MISSOURI, ASSIGNOR TO THE HOKE EN- GRAVING PLATE COMPANY, OF MISSOURI RELIEF=TYPE PRODUCTION.

SPECIFICATION forming part of Letters Patent No. 388,361, dated. August 21, 1888.

Application filed March 30, 1885. Serial No.160,fi76. (No model.) Patented in England November 96, 1887, No,16,304.

To all whom it may concern.-

Be it known that I, JosErH W. HoKE, of St. Louis, Missouri, have made a new and useful Improvement in Relief-Type Production, of which the following is a full, clear, and exdescription.

Relieftypes of the class to which the present improvement relates are cast, molded, electrotypcd, or prepared in a matrix formed out of a composite engravingplate consisting of a base-plate having a plane, smooth, hard surface, to which is applied a coating that is softer than the base-plate and of pulverizable material which can be readily scored and engraved by means of a graver and which crumbles under the graver, and the matrix is formed by engraving the design of the desired type in the coating, the lines engraved being extended through the coating to the base plate beneath. From such engraved matrices stereotypes were cast directly as early as the latter part of the last century. A coated plate, to be used as a matrix when engraved, was patented by Hoffman in France in 1792. Like his successors, Hoffman used a comparatively soft coating upon a hard baseplate, the thickness of the coating regulating the relief and the base-plate equalizing the depth of the engraved lines. Palmer, Joyce, and others in Europe and this country have substantially followed Hoifman but all have failed to produce a satisfactory engraving-plate for the purpose described. The various coatings which have been devised are objectionable for many reasons, and especially because theparticles of the coating cohere more to each other than to the base-plate, and in consequence the coating, when out with the graver, scales from the base-plate and chips, so that it is impracticable to form the cuts closely together, or to cross them, or to do any but the coarsest work with the plates.

To obviate this difficulty, as well as to provide an engraving-plate having other superior qualities, is the aim of this improvement.

The base-plate of my improved engravingplate for stereotyping purposes is preferably a polished blued steel plate of suitable superficies. it withstands the heat incident to stereotyping, and its tint, when a light-colored coating is used, presents a marked and agree able contrast to the coating and enables the engraver to readily judge the effect of his work. For electrotyping purposes a bascplate of glass is preferred. Glass is also an excellent material in combination with the special coating preferred by me and heroinafter described, and its transparency enables the engraver to examine his work by holding the plate to the light.

For the coating ofthe plate a finely-powdered materialsuch as a finely-powdered earth or mixture of earths or other equivalent finelypowdered inorganic substance or substances which will withstand the heat of molten stereotyping metali s used. The more thoroughly and evenly the material is comminuted and the more marked the contrast in color between the coating and the base-plate the better is the engraving-plate adapted for the purpose in view.

The leading features of the improvement are, that the particles of the coating next to the base-plate adhere thereto more strongly than the particles above them adhere either to them or to each other, and that the coating is very friable and the particles thereof very loosely as well as very evenly bonded together, so thattheyreadilyseparatewithoutcakingand without breaking away between the lines when the plate is engraved; bonding the particles of the coating to each other and to the baseplate with soluble glass or an equivalent soluble mineral alkaline bond; bonding theparticles of the coating to each other and to the baseplate by treating the particles with a solution of soluble glass or equivalent soluble mineral alkaline solution, and then baking the coated base-plate until the coating is dried; mixing together the ingredients to be bonded, then adding a water-glass in solution or an equivalent solution of asolublc mineral alkalinesubstance, and then baking or subjecting a baseplate coated with the mixture to a heat beneath the boiling-point and not funnier-100 Fahrenheit until the coating is solidified, after which the heat may be increased without injury to the coating; the special combination of substances given in the formula and used to form the coating upon the baseplate.

2' sstsei The annexed drawings, making part of this specification, exhibit an engraving-plate of the kind under consideration.

Figure 1 is a plan view. Fig. 2 is a longitudinal section of Fig. l on line 2 2,

A represents the baseplate, and B represents the coating.

The same letters of reference denote the same parts.

In engraving a design in the matrix it is highly desirable that the engraver shall be able to see distinctly the lines made through the coating, and thereby judge correctly the work being done. To this end the coating is made white or light colored, while the surface of the base-plate appears dark, and the end is more effectually attained by employing a blood stillplate for the base-plate.

The production of a perfect type requires corresponding perfection in the matrix in which the type is cast or otherwise prepared. A plane, smooth, polished metallic plate, A, presents the surface required for the face of the type. To obtain a sufficient counter for the type, the coating B must be of corresponding thickness, and to makesmooth fine lines, to make lines close together,and to cross the lines the coating must not break away between the lines nor where they cross each other. It is also desirable to minimize the resistance to the point of the graver as it is moved through the coating. It is also desirable for the coating to be very even and homogeneous,so that whether slightly harder or slightly softer it shall offer uniform resistance to the graver. It is not only essential that the coating withstand the heat of stereotyping or the acid in eleetrotyping, but it is also very desirable that it resist the action of the water or of the atmosphere, so that, whether recently made or for some time on hand, it shall be capable of use, and the merchant-able qualities of the plate are enhanced ifit is light, portable, and cheap. All these requisites, and most of them notably,are attained with my improved coating, whose most desirable constitution is stated in the following formula: Of sulphate of barium, (barytes,) take two drams; of silicate of magnesia, (French chalk,) take one dram; of silicate of soda, take four drops; and of water, take five cubic centimeters. This mixture will cover sufficiently thick six square inches of plate. The more perfectly it is mixed the better the plate. A good way to make the mixture is first to mix the earth or earths in a finely-pulverized form with water and work and rub the ingredients in a mortar until the mixture becomes smooth, and then add the solution of soluble glass and mix it with the other ingredients as thoroughly as practicable. The mixture should then be spread evenly over the base-plate, shaking it slightly to settle the coating evenly. The coating should, after being placed on the plate, be dried by heat beneath the boiling-point and not lower than 100 Fahrenheit, and preferably between 180 and 190 Fahrenheit, until it solidifies, after which the heat may be increased as high as 300 Fahrenheit Without injury to the coating. The object in keeping the heat beneath the boiling-point while the coating remains in a semi-liquid state is to prevent its boiling. The coating should be thoroughly dried. coating at its top is usually incrusted, and after the plate has cooled and before it is engraved the crust should be scraped off and the coating made of a uniform depth over the surface of the base-plate.

When the coating is mixed very slowly, it may be baked at once; but otherwise it should be allowed to stand after mixing for at least five minutes before baking, and is rather improved by being allowed to stand longer. The

The

object in allowing it to stand before baking is to allow the air contained in the mixture to escape as far as possible and to prevent the coating from curling up and cracking while being dried.

The above method of mixing and baking is not the only one that can be used. The essential points are first to introduce the bond in the form of a solution into the body of the coating, and then dry the coating upon the plate.

Instead of mixing the bond with the water and earths in the manner above described,the mixture may be made without the bond and dried, with or without artificial heat, upon the base-plate, and the coating may then be saturated with a solution of silicate of soda containing from twenty-five to fifty drops of silicate of soda to an ounce of water, and then baked as first above directed. In this process I prefer to use twenty-fivc drops of the silicate of soda to an ounce of water.

Though I consider the formula for the coating above given the best, it may be widely departed from and good results still obtained, so long as the bond is of the proper nature and is used in the proper proportion. I prefer to use the earths named in the formula (silicate of magnesia and'sulphate of barium) and in the proportions given; but the proportions may be varied indefinitely and good, though inferior,plates made. Either silicate of magnesia or sulphate of barium may be used alone in place of the mixture, though not so good. Sulphate of barium is somewhat undesirable when used alone, because a coating made of it has a tendency to crack in drying.

The following substances are unsuitable as substitutes for sulphate of barium and silicate of magnesia, viz: first, all soluble salts; second, alkalies, including earthy alkalies or alkaline earths; and, third, all substances incapable of withstanding the heat of molten type-metal in stereotyping. All other solid inorganic substances which can be reduced to a fine powder, except the metals, I call earths, and wherever the word earth or earthy is used in this specification it should be understood in that sense and subject to the above limitations. Among the substances which I call earths is silica, sometimes called an acid, but for sessei my purposes it has all the qualities of an earth, and I find the silicious rocks especially valuable.

All kinds of light-colored earths may, when finely powdered, be used in lieu of the ones named in the above formula, though they are far from being equally good. Those which have the least attraction for water are the best. The clays areperhaps the least desirable ofall, because of their tendency to crack when drying. It is desirable where they are used to mix them with an equal bulk of plaster-ofparis or with some other substance which will prevent cracks, as the bond will not perform that function when used in the proper propor tion.

The most desirable earths-naming them in their order of merit-are, in my opinion, the following: soapstone, tripoli, tale, quartz, and chalk. They may be used singly or in combination with each other or other white earths not named. Sulphate of barium, though excellent when mixed with silicate of magnesia, is not'so good as the substances named above when used singly. I have obtained my best results by mixing a very light with a very heavy earth, and consider that a good course to follow. I consider the specific gravity of a mixture of sulphate of barium and silicate of magnesia in the proportions named in the formula given the most desirable, and in se lecting an earth or making a mixture of earths an attempt to approximate the same specific gravity should be made.

I have given the proportions of silicate of soda and water which I prefer to use with the mixture of earths given in the formula; but both water and the bond may be used in different proportions, though the results will not be so good. From four tosix (6) cubic centimeters of water and from one to fourteen drops of silicate of soda may be used with the mixture of earths given in the formula. Vhere, however, less than two drops of bond are used, the plate is very poor, because insufiiciently bonded. \Vhere more than eight drops are used, the coating is made too hard to be entirely satisfactory, and is more or less liable to break away from the baseplate when being engraved.

The silicate of soda which I have used and which I have taken as a standard in making out the formula given is the solution known commercially as pure silicate of soda. It is not necessary that it should be strictly chemically pure. It sometimes differs somewhat in density and purity from the usual standard; but I have never known it to differ enough to make the above formula and directions inapplicable.

\Vhat is commercially known as pure solution of silicate of potash, and which shares the name of soluble glass with silicate of soda, is a strict chemical equivalent of silicate of soda, and may be substituted for it and the same proportions used where the solution is of the same specific gravity as the pure solution of silicate ofsoda. There are also other soluble alkaline mineral equivalents ofsilicate of soda, as is well known.

The following rule may be taken as a guide in using the bond and water with other earths or mixtures of earths than the mixture prescribed in my formula: The amount of bond and water used should be the same as for an equal bulk of the mixture of earths given in the formula. This rule is not exact, because the chemical character of the different earths varies; but it will answer for practical purposes. Another test as to the amount of wa ter to be used is that the mixture when made should be thin enough to pour out ofa containing-vessel, but no thinner than necessary for that purpose. It should be of about the consistency of batter, so that a small portion will cling to the side of the vessel from which it is poured. Clay is an exception to the general rule as to the amount of water necessary. XVhcre it is used, only one-half the quantity of water necessary for other substances should be used.

here more water than I have directed to be used is used, the earths settle to the bottom and the larger portion of the bond remains on top, so that there is an insufficient amount of bond near the base-plate unless an unnecessary amount of bond is used. The amount of bond directed to be used is what should be embodied in the coating.

I desire not to be limited to any special composition or bond. I was the first to discover the desirability of bonding the particles of the coating Very loosely together and more strongly to the base-plate than to each other, as well as a method of accomplishing that end. There are well-known chemical equivalents of soluble glass, all of which may be used. Some are called soluble glasses, though I only use the term soluble glass in this specification as embracing within its meaning silicate of soda and silicate of potash in solution. I desire to cover all equivalents.

I claim 1. As a new article of manufacture, an engraving-plate having a base-plate with a smooth, hard upper surface and a soft, friable coating of minute particles of powdered matter loosely bonded together and having those particles of the coating next the base plate more strongly bonded to it than the particles above them are bonded either to them or to each other.

2. Asa new articleot'manufacture,an engraving-plate composed of a base-plate having a smooth, hard upper surface, a soluble mineral bond, and asot't, friable coating of fine earthy particles loosely bonded together and more strongly bonded to the base-plate by said soluble mineral bond, so that the particles of the coating next the baseplate adhere thereto more strongly than the particles above them adhere either to them or to each other, as and for the purposes described.

3. As a new article of manufacture, an en- IOC graving-plate having a soft, friable coating composed of minute earthy particles bonded together and to a base-plate having a smooth, hard upper surface by soluble glass, for the purposes set forth.

4. In combination with a base-plate having a smooth, hard upper surface, a coating composed of soluble glass, silicate of magnesia, and sulphate of barium, in substantially the proportions herein recommended, as and for the purposes described.

5. In combination with a base-plate having a smooth, hard, upper surface of soluble glass and a mixture of pulverized earths of different specific gravities, as and for the purposes described.

6. The herein-described process of making an engraving-plate having a coating bonded by a soluble glass, consisting in introducing a base-plate by heat, and finally removing the 30 crust, all substantially as herein directed.

JOSEPH W. HOKE.

Witnesses:

(J. D. MooDY, FREDERICK SWAINE.

Affidavit having been filed showing that no foreign patent had been granted for the invention described in the specification annexed to Letters Patent No. 388,361, granted August 21, 1888, upon the application of Joseph W. Hoke, of St. Louis, Missouri, for an improvement in Relief-Type Production previous to the date of granting said patent, it is hereby certified that the words subject to the limitation prescribed by Section 4887, Revised Statutes, by reason of English Patent dated November 26, 1887, No. 16,301 at the end of the grant, and the words Patented in England November 26, 1887, No. 16,304, at the head of the specification, should be stricken out; and it is further certified that in line 5, page 1, the syllable exshould be stricken out and the Word eavaet inserted instead; in line 17, page 2, the Word still should be stricken out and the Word steel inserted instead, and in line 13, page 4, the Word of should be stricken out, and that the said Letters Patent should be read with these corrections therein that the same may conform to the record of the case in the Patent Office.

Signed, countersigned, and sealed this 25th day of September, A. D. 1888.

[SEAL] D. L. HAWKINS,

Assistant Secretary of the Interior.

Countersigned:

BENTON J. HALL,

Commissioner of Patents. 

